This invention relates to a method and apparatus for transmitting a stream of data packets over one or more physical channels.
A physical channel is a transmission path as, for example, a fiber optic cable, a two-wire copper line, or a radio wave transmission path. A number of standards exist for the format and transport of data packets, for example, asynchronous transfer mode (ATM), transport control protocol/internet protocol (TCP/IP), point to point protocol (PPP), and serial line interface protocol (SLIP). With such standards, data packets are typically routed from a transmitter to a receiver by mapping the packets to a physical channel. Where the receiver does not acknowledge receipt of packets, some protocols (such as TCP/IP) assume this is due to congestion and the transmitter responds by repeatedly sending the data choosing ever smaller data windows (which are blocks of data) during each transmission.
U.S. Pat. No. 5,463,629 issued Oct. 31, 1995 to Ko concerns an ISDN line. In Ko, if a physical channel would be congested with a data stream (i.e., it would have insufficient bandwidth), the data stream is piped to a virtual channel. A mechanism is then provided to map the virtual channel to two physical channels.
U.S. Pat. No. 5,608,733 issued Mar. 4, 1997 to Vallee addresses congestion in an ATM network by sending cells (i.e., data packets) of a data stream over several physical links in a round robin fashion and then re-assembling the data stream in proper order at the receiver.
Congestion is only one reason for degradation of a communications link. Errors in the transmission, intermittent connectivity, and high channel latency are other potential problems.
This invention seeks to overcome drawbacks of known systems for transmitting a single data stream.